Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Brian Gerst <> | Subject | [PATCH 6/9] x86/boot/64: Remove inverse relocations | Date | Mon, 23 Oct 2023 17:17:27 -0400 |
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Now that the percpu section is not at a fixed virtual address, inverse relocations, which were needed to offset the effects of relocation on RIP-relative percpu references, are no longer needed.
Signed-off-by: Brian Gerst <brgerst@gmail.com> --- arch/x86/boot/compressed/misc.c | 14 +--- arch/x86/tools/relocs.c | 126 +------------------------------- 2 files changed, 2 insertions(+), 138 deletions(-)
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index b99e08e6815b..2de345a236c0 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -221,7 +221,7 @@ static void handle_relocations(void *output, unsigned long output_len, /* * Process relocations: 32 bit relocations first then 64 bit after. - * Three sets of binary relocations are added to the end of the kernel + * Two sets of binary relocations are added to the end of the kernel * before compression. Each relocation table entry is the kernel * address of the location which needs to be updated stored as a * 32-bit value which is sign extended to 64 bits. @@ -231,8 +231,6 @@ static void handle_relocations(void *output, unsigned long output_len, * kernel bits... * 0 - zero terminator for 64 bit relocations * 64 bit relocation repeated - * 0 - zero terminator for inverse 32 bit relocations - * 32 bit inverse relocation repeated * 0 - zero terminator for 32 bit relocations * 32 bit relocation repeated * @@ -249,16 +247,6 @@ static void handle_relocations(void *output, unsigned long output_len, *(uint32_t *)ptr += delta; } #ifdef CONFIG_X86_64 - while (*--reloc) { - long extended = *reloc; - extended += map; - - ptr = (unsigned long)extended; - if (ptr < min_addr || ptr > max_addr) - error("inverse 32-bit relocation outside of kernel!\n"); - - *(int32_t *)ptr -= delta; - } for (reloc--; *reloc; reloc--) { long extended = *reloc; extended += map; diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c index 01efbfdd3eb3..7feb63179b62 100644 --- a/arch/x86/tools/relocs.c +++ b/arch/x86/tools/relocs.c @@ -28,7 +28,6 @@ struct relocs { static struct relocs relocs16; static struct relocs relocs32; #if ELF_BITS == 64 -static struct relocs relocs32neg; static struct relocs relocs64; #define FMT PRIu64 #else @@ -84,7 +83,6 @@ static const char * const sym_regex_kernel[S_NSYMTYPES] = { "__initramfs_start|" "(jiffies|jiffies_64)|" #if ELF_BITS == 64 - "__per_cpu_load|" "init_per_cpu__.*|" "__end_rodata_hpage_align|" #endif @@ -281,33 +279,6 @@ static const char *sym_name(const char *sym_strtab, Elf_Sym *sym) return name; } -static Elf_Sym *sym_lookup(const char *symname) -{ - int i; - for (i = 0; i < shnum; i++) { - struct section *sec = &secs[i]; - long nsyms; - char *strtab; - Elf_Sym *symtab; - Elf_Sym *sym; - - if (sec->shdr.sh_type != SHT_SYMTAB) - continue; - - nsyms = sec->shdr.sh_size/sizeof(Elf_Sym); - symtab = sec->symtab; - strtab = sec->link->strtab; - - for (sym = symtab; --nsyms >= 0; sym++) { - if (!sym->st_name) - continue; - if (strcmp(symname, strtab + sym->st_name) == 0) - return sym; - } - } - return 0; -} - #if BYTE_ORDER == LITTLE_ENDIAN #define le16_to_cpu(val) (val) #define le32_to_cpu(val) (val) @@ -750,75 +721,8 @@ static void walk_relocs(int (*process)(struct section *sec, Elf_Rel *rel, } } -/* - * The .data..percpu section is a special case for x86_64 SMP kernels. - * It is used to initialize the actual per_cpu areas and to provide - * definitions for the per_cpu variables that correspond to their offsets - * within the percpu area. Since the values of all of the symbols need - * to be offsets from the start of the per_cpu area the virtual address - * (sh_addr) of .data..percpu is 0 in SMP kernels. - * - * This means that: - * - * Relocations that reference symbols in the per_cpu area do not - * need further relocation (since the value is an offset relative - * to the start of the per_cpu area that does not change). - * - * Relocations that apply to the per_cpu area need to have their - * offset adjusted by by the value of __per_cpu_load to make them - * point to the correct place in the loaded image (because the - * virtual address of .data..percpu is 0). - * - * For non SMP kernels .data..percpu is linked as part of the normal - * kernel data and does not require special treatment. - * - */ -static int per_cpu_shndx = -1; -static Elf_Addr per_cpu_load_addr; - -static void percpu_init(void) -{ - int i; - for (i = 0; i < shnum; i++) { - ElfW(Sym) *sym; - if (strcmp(sec_name(i), ".data..percpu")) - continue; - - if (secs[i].shdr.sh_addr != 0) /* non SMP kernel */ - return; - - sym = sym_lookup("__per_cpu_load"); - if (!sym) - die("can't find __per_cpu_load\n"); - - per_cpu_shndx = i; - per_cpu_load_addr = sym->st_value; - return; - } -} - #if ELF_BITS == 64 -/* - * Check to see if a symbol lies in the .data..percpu section. - * - * The linker incorrectly associates some symbols with the - * .data..percpu section so we also need to check the symbol - * name to make sure that we classify the symbol correctly. - * - * The GNU linker incorrectly associates: - * __init_begin - * __per_cpu_load - * - * The "gold" linker incorrectly associates: - * init_per_cpu__gdt_page - */ -static int is_percpu_sym(ElfW(Sym) *sym, const char *symname) -{ - return 0; -} - - static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, const char *symname) { @@ -829,12 +733,6 @@ static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, if (sym->st_shndx == SHN_UNDEF) return 0; - /* - * Adjust the offset if this reloc applies to the percpu section. - */ - if (sec->shdr.sh_info == per_cpu_shndx) - offset += per_cpu_load_addr; - switch (r_type) { case R_X86_64_NONE: /* NONE can be ignored. */ @@ -843,33 +741,21 @@ static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, case R_X86_64_PC32: case R_X86_64_PLT32: /* - * PC relative relocations don't need to be adjusted unless - * referencing a percpu symbol. + * PC relative relocations don't need to be adjusted. * * NB: R_X86_64_PLT32 can be treated as R_X86_64_PC32. */ - if (is_percpu_sym(sym, symname)) - add_reloc(&relocs32neg, offset); break; case R_X86_64_PC64: /* * Only used by jump labels */ - if (is_percpu_sym(sym, symname)) - die("Invalid R_X86_64_PC64 relocation against per-CPU symbol %s\n", - symname); break; case R_X86_64_32: case R_X86_64_32S: case R_X86_64_64: - /* - * References to the percpu area don't need to be adjusted. - */ - if (is_percpu_sym(sym, symname)) - break; - if (shn_abs) { /* * Whitelisted absolute symbols do not require @@ -1083,7 +969,6 @@ static void emit_relocs(int as_text, int use_real_mode) /* Order the relocations for more efficient processing */ sort_relocs(&relocs32); #if ELF_BITS == 64 - sort_relocs(&relocs32neg); sort_relocs(&relocs64); #else sort_relocs(&relocs16); @@ -1115,13 +1000,6 @@ static void emit_relocs(int as_text, int use_real_mode) /* Now print each relocation */ for (i = 0; i < relocs64.count; i++) write_reloc(relocs64.offset[i], stdout); - - /* Print a stop */ - write_reloc(0, stdout); - - /* Now print each inverse 32-bit relocation */ - for (i = 0; i < relocs32neg.count; i++) - write_reloc(relocs32neg.offset[i], stdout); #endif /* Print a stop */ @@ -1172,8 +1050,6 @@ void process(FILE *fp, int use_real_mode, int as_text, read_strtabs(fp); read_symtabs(fp); read_relocs(fp); - if (ELF_BITS == 64) - percpu_init(); if (show_absolute_syms) { print_absolute_symbols(); return; -- 2.41.0
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